That is incorrect. You can manufacture your own as long as it is not for resale.
From the ATF FAQ:
May I lawfully make a firearm for my own personal use, provided it is not being made for resale?
Firearms may be lawfully made by persons who do not hold a manufacturer’s license under the GCA provided they are not for sale or distribution and the maker is not prohibited from receiving or possessing firearms. However, a person is prohibited from assembling a non-sporting semiautomatic rifle or shotgun from 10 or more imported parts, as set forth in regulations in 27 C.F.R. 478.39.
In addition, the making of an NFA firearm requires a tax payment and advance approval by ATF. An application to make a machinegun will not be approved unless documentation is submitted showing that the firearm is being made for the official use of a Federal, State, or local government agency (18 U.S.C. § 922(o),(r); 26 U.S.C. § 5822; 27 C.F.R. §§ 478.39, 479.62, and 479.105).
http://www.criminaldefenselawyer.com/resources/can-i-sell-or-give-my-homemade-gun-another-person.htm
The Gun Control Act of 1968 (GCA) permits an unlicensed individual to make a firearm for personal use, but not for sale or distribution. However, the law does not explicitly preclude an unlicensed person from later selling, giving away, or otherwise transferring a homemade firearm to another person as long as it was originally intended for personal use. A gun explicitly made for personal use can be sold or transferred in the same way that a factory-made firearm of that same class can be sold or transferred.
The Gun Maker’s Original Intent
The key in determining whether a homemade gun can be legally sold or transferred rests with knowing the intent of the maker when the gun was first created. Relevant factors in determining the transferor’s intent may include: the length of time between the creation of the firearm and its transfer; the specific reason for the sale or transfer; and whether the maker of the firearm frequently sells or transfers homemade firearms. For example, a time lapse between creation and sale of many years, a reason for sale that has no sinister overtones, and a transfer that is one-in-a-lifetime for the transferor, would indicate an original intent to keep the gun. By contrast, quickly transferring a gun right after its creation, to someone who could not legally possess a firearm, by someone who regularly transfers such guns, would indicate a lack of intent to keep the gun.